Coast Guard regulations in the United States and most foreign countries require vessels over a certain size or carrying a certain number of passengers to have life boats or life rafts on board in case of emergency. The presently more-popular alternative is to carry inflatable life rafts because of the relatively small amount of storage space required when the rafts are in a deflated condition. The presently-used life rafts come in a variety of sizes and shapes, including oblong, square, circular, or substantially circular multi-sided, depending upon the number of occupants they are designed to carry. These rafts are typically made of a rubber or rubberized flexible material and include air chambers which, when fully inflated, provide relatively rigid sidewalls. For protection against severe weather, most of these life rafts include a canopy cover which is supported by inflatable tubes which also become relatively rigid when fully inflated.
Typically, the inflatable life rafts include a compressed gas canister which may be manually or automatically activated to inflate the air chambers of the raft. Unfortunately, the rafts will not necessarily inflate in an upright position and, if overturned upon inflation, must be righted before they can be occupied.
Present Coast Guard requirements specify that approved life rafts must be capable of being uprighted by a single person in the water. While this can usually be accomplished by a healthy individual in calm water, this cannot necessarily be accomplished in rough or extremely cold water or by an person who is injured or fatigued. Such adverse conditions are not entirely unlikely to occur when a vessel is sinking on navigable waters.
The presently commonly-used type of inflatable life raft has not significantly changed in general design since about 1948. British Patent Specification No. 864,382, published Apr. 6, 1961, suggest making an inflatable canopy shaped substantially in the form of a sphere and to arrange the center of gravity to be below the geometric center so that the raft will be self-righting. Due to the large amount of material required to construct such a canopy, the cost of such a structure is considerable. Also, in order to cause the canopy to have buoyancy sufficient to overcome the mass of the raft, a canopy or canopy support of this shape is relatively massive itself. Furthermore, when subjected to rough seas and high winds, the significant surface area of such a structure can make it vulnerable to being tossed and rolled upon the water.